Robert De Niro's lawsuit against his ex-assistant is getting nastier -- he now claims she made veiled threats against him, if he didn't ante up on her demands.
According to new legal docs, obtained by TMZ, the famed actor says Graham Chase Robinson sent him an email in August 2019 claiming she would disclose personal info about him. He insinuates it's no coincidence she sent that when she did, because just days later he sued her for misusing the company credit card and binge-watching "Friends" on the job.
He also claims that in a separate email Robinson threatened to write a memoir containing personal information about De Niro if, again, her demands weren't met. In the docs, De Niro doesn't specify Robinson's alleged demands.
What's more ... De Niro claims Robinson only counter-sued him in October -- alleging harassment and discrimination -- because he called her out for her work misconduct.
De Niro denies making sexually-charged comments and, as we first reported, De Niro's attorney, Tom Harvey, called the allegations "beyond absurd."
De Niro, however, does admit leaving her the angry voicemail ... which Robinson had included in her lawsuit.